With the proliferation of various types of computing devices and computing applications, varied types of input devices have also proliferated. In the computing world an input device is a piece of computer hardware that is used to provide data and control signals to an information processing system. Examples of input devices include, for example, keyboards, mice, scanners, digital cameras, and joysticks, among others. Input devices can be classified by mode of input, whether the input generated by the device is discrete or continuous, and the number of degrees of freedom involved (e.g., two dimensional or three dimensional).
As discussed above, input devices include mice, which are a type of pointing input device. A pointing device is any type of human interface device that allows a user to input spatial data into a computer. In the case of a typical mouse, a two dimensional input device, this is usually done by detecting movement across a physical surface. Three dimensional pointing devices also exist and these operate by reporting their angle of deflection. In both of these cases, movements of the pointing device are echoed on a screen or other display device by movements of a pointer on the display.
Sometimes input devices can be combined to allow for two different types of input. For example, joysticks and buttons are often combined on video game controllers.
Devices can be used for sensing. Such sensing devices can be used, for example, for sensing biological signals such as heart rate and galvanic skin response, as well as physical phenomena such as acceleration and orientation.